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Question for the professional builders: 400 small block, AFR heads without steam holes in them.
Will this be a problem for a street car?
A local midwest well-knwon race engien builder had said it would e OK, he passed 6 years ago.
The engine owner would like a little more confidence before I start it fo rthe first time. H eis considering pullign them and drillign them.
 

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I’ve done a handful of 400 based builds without steam holes drilled in the heads. One of them is a 406 with 195 AFR’s. It’s been going strong for over 10 years now with no overheating issues at all. The 421 I run in my my car is a dart block with steam holes, but none in the AFR heads. No issues.
 

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I have a set of afr heads and I did drill mine as the paperwork said to do it
Motor has 4000 ish miles on it and runs like a top
 

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just starting a 400 build for my '74. it's got a 350 now with 305 heads. Pretty strong just drippy. I hope the one I put together I can seal up and not drip.

ALL the info I see says to make power it's mostly in the heads how they flow and swirl the air fuel mix. looking for about 400 hp out of the build. using stock crank, rods. and block pistons will depend on weather I need to bore it or not. working on cam and heads now. any suggestions? new Dart or reworked stock 400 heads. I'd love the input thanks
 

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just starting a 400 build for my '74. it's got a 350 now with 305 heads. Pretty strong just drippy. I hope the one I put together I can seal up and not drip.

ALL the info I see says to make power it's mostly in the heads how they flow and swirl the air fuel mix. looking for about 400 hp out of the build. using stock crank, rods. and block pistons will depend on weather I need to bore it or not. working on cam and heads now. any suggestions? new Dart or reworked stock 400 heads. I'd love the input thanks
Other than Vortec heads, there isn't a stock head worth the cost of rebuilding them anymore, not when you can get a decent imported aluminum head casting for under $180/each bare that is a copy of the Dart Pro-1 Platinum 200cc w/64 to 68cc chambers. Sold under a bunch of different "white box" names but is the same casting used by AFR for their new as-cast Enforcer heads. Surprisingly nice import casting, IMO better than Edelbrock or the DART it is copied from.
Shop well and if you can assemble them yourself you can get them up and running for a flat tappet hydro or solid for under $650 complete. Hydro roller for $700
If you need source links for the castings and completion parts just ask.

The stock 400 heads would be a total waste of time, those are just smog era open chamber crap heads. Cost you close or the same to rebuild old junk heads as it would be to get a basic entry level aluminum head that will be a whole lot better.
 

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Other than Vortec heads, there isn't a stock head worth the cost of rebuilding them anymore, not when you can gewt a decent imported aluminum head casting for under $180/each bare that is a copy of the Dart Pro-! Platinum 200cc w/64 to 68cc chambers. Sold under a bunch of different "white box" names but is the same casting used by AFR for their new as-cast Enforcer heads. Surprisingly nide import casting, IMO better than Edelbrock or the DART it is copied from.
Shop well and if you can assemble them yourself you can get them up and running for a flat tappet hydro or solid for under $650 complete. Hydro roller for $700
If you need source links for the castings and completion parts just ask.

The stock 400 heads would be a total waste of time, those are just smog era open chamber crap heads. Cost you close or the same to rebuild old junk heads as it would be to get a basic entry level aluminum head that will be a whole lot better.
I'll gladly take the links for the heads you're talking about. My brother has a 350 he's trying to hop up on a budget, the heads are currently 993 heads with small valves that are junk.
 

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I always drill the heads for the steam holes.
We always did at the Machine shop. I still do. I guess it just falls under we always did and keep doing it whether its needed or not anymore. We had to make the engines fool proof, so if it didn't hurt to have them, but it MAY to not, we did it.
 

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I'll gladly take the links for the heads you're talking about. My brother has a 350 he's trying to hop up on a budget, the heads are currently 993 heads with small valves that are junk.
Here is the current best price source, seller with best price shanges on a weekly basis almost, and on Amazon also...but if you know how to spot the casting by it's identifying features it is easy to spot the good imported casting. You'll find it listed as 195cc, 198cc, 200cc and 205cc depending on whatever seller is trying to get an edge in the market...but it has been verified to be a poured and measured 198cc port.
Identifying features on the casting to tell it from other , lesser quality imports...the triangle and "W" shaped water jacket holes in the deck face, the "Fat" upper corners of the valve cover rail, the straight lower edge across the bottom of the area that would be under the exhaust crossover port in a stock SBC head's intake gasket face, and the solid exhaust port face with no releif between the end ports and center ports.

This is the straight plug version, with Gen 1 intake manifold pattern only.

There is also a angle plug version, with both Gen 1 and Vortec intake bolt patterns....but check to make sure whatever you plan to put these into has headers available that fit your chassis and angle plugs, as a lot of common street headers don't fit angle plug heads and the would force you into more expensive race headers.

They come with seats cut for 2.02 and 1.6" valve size, but you can re-cut up to a 2.08" intake valve if you want. Good casting for a guy who wants to do home port work, easy to improve it 25 cfm on the intake side with even basic skill doing a cartridge roll blending, getting them to 275cfm which gives easy 550 HP potential on a 383 or 406.

Good source for the parts needed to assemble them, Competition Products, listed as "Head Improvement Kits, with various valve size combinations and various levels of valvesprings depending on what you need.
Basic flat tappet kit is typically $169, but seems inventory is low at the moment,probably a Covid thing....but there is also Alex's Parts for good deals on valvetrain stuff too.
Here is a mechanical flat tappet/hydraulic roller spec kit for iron heads, you'd just have to add spring seats to use it on aluminum heads....$199

Including buying rocker studs and guideplates your still under $650 for all of it, ready to assemble..
 

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Other than Vortec heads, there isn't a stock head worth the cost of rebuilding them anymore, not when you can gewt a decent imported aluminum head casting for under $180/each bare that is a copy of the Dart Pro-! Platinum 200cc w/64 to 68cc chambers. Sold under a bunch of different "white box" names but is the same casting used by AFR for their new as-cast Enforcer heads. Surprisingly nide import casting, IMO better than Edelbrock or the DART it is copied from.
Shop well and if you can assemble them yourself you can get them up and running for a flat tappet hydro or solid for under $650 complete. Hydro roller for $700
If you need source links for the castings and completion parts just ask.

The stock 400 heads would be a total waste of time, those are just smog era open chamber crap heads. Cost you close or the same to rebuild old junk heads as it would be to get a basic entry level aluminum head that will be a whole lot better.
Ericnova I agree with you 100% I just had Straub Tech do exactly what you posted, they got the bare castings and Scott assembled them with all the best components and It was under 1200.00 I believe with gaskets. Chris Straub told me they are good as AFR's for way less money.
 

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Ericnova I agree with you 100% I just had Straub Tech do exactly what you posted, they got the bare castings and Scott assembled them with all the best components and It was under 1200.00 I believe with gaskets. Chris Straub told me they are good as AFR's for way less money.
Question for the professional builders: 400 small block, AFR heads without steam holes in them.
Will this be a problem for a street car?
A local midwest well-knwon race engien builder had said it would e OK, he passed 6 years ago.
The engine owner would like a little more confidence before I start it fo rthe first time. H eis considering pullign them and drillign them.
Question for the professional builders: 400 small block, AFR heads without steam holes in them.
Will this be a problem for a street car?
A local midwest well-knwon race engien builder had said it would e OK, he passed 6 years ago.
The engine owner would like a little more confidence before I start it fo rthe first time. H eis considering pullign them and drillign them.
I've done (drilled) many of these heads (as a professional engine builder) and feel the trade off is gasket retention strength vs. cooling around the exhaust valve area. If in a iron head with less than 4.155 bore many stock gaskets will seal fine for long periods of time with the steam holes drilled per OEM location. When bores are big and heads are modified then gasket quality and fit becomes very important. How the engine is run is a factor too. IF in a road race car or endurance off road situation you need the holes because exhaust heat will create steam which cannot cool the head. OR in a truck pulling a trailer. If you have an over bored 400 block analyzing which factor hurts you the most - gasket leakage of combustion pressure into the coolant via the steam hole, or steam boiling creating an overheated valve seat and crack is your game plan. Or doing an upgrade to an MLS gasket set with appropriate deck surface finishes.

I have personally owned K series 3/4 and 1 ton suburbans and trucks used very hard pulling loads for up to 300,000 miles service before any overhaul. Those gaskets were leaking at the steam holes a bit - but not of any operational consequence compared to the bore wear or tired heads. Aluminum heads move around more and scuff the gasket more. They won't hold up to extreme mileage before failure, but very few people put extreme mileage on these old engines anymore so it is a problem that has mostly gone away - especially with MLS gaskets now available.

I cannot imagine in a Nova chassis you could load the engine hard enough, long enough, to have a steam hole issue either way, unless you run the long track at Bonneville.
 

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for what it's worth, on applications that don't have the block holes plugged for race use, I typiccally still only drill the lower hole since that is really the only spot a steam pocket could get trapped if you look at the V shape of the engine block.
Many of the aftermarket aluminum heads you can't get to water jacket in the upper hole anyway, many are cast solid there and despite any drill angle you still with never hit water jacket., just solid metal until your drill breaks out in the valvecover area!!
 

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Question for the professional builders: 400 small block, AFR heads without steam holes in them.
Will this be a problem for a street car?
A local midwest well-knwon race engien builder had said it would e OK, he passed 6 years ago.
The engine owner would like a little more confidence before I start it fo rthe first time. H eis considering pullign them and drillign them.
I also agree with Ericnova, I built a 400 with Flowtec aluminum heads. The speed shop/machine shop I had do my machine work drilled only the lower holes and I’ve had zero problems with overheating even when cruising the fairgrounds on a 95 degree day.😁
 

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Discussion Starter #14
I really should have proofread all my bad typing!!
I am not sure of the engine bore, he doesn't talk about it, I'm thinking 434.
It is in a 69 Camaro protouring, he is over 70 and has no plans to autocross it but his son would in a second.
I am finishing the exhaust and am ready to start it for the first time. He is having second thoughts and wants to buy new AFR angle plug heads, there is a minor plug boot clearance issue with straight plugs. I don't think it is worth the time and expense to switch heads.
 
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