Hi, I got a 429 with a d0ve-a block and d0ve-c heads. As far as I know this engine is all stock and has never been tore apart. From what I have been researching it should have around 10.5 to 11.0 compression and everyone says that you cant even run 93 octane in this. Is it true? If it is, what would I have to do? My second question is what would be the easiest way to get up into at least the four hundred horsepower range?
For 400 horse, if you are starting with what was called a "Thunderjet" motor with 11:1 compression, you just need a cam and probably a good set of headers. Maybe a little bigger 4bbl carb. They were rated at 360 hp under the SAE gross HP ratings. Net is supposed to be 80%, or 288 horse, so perhaps the 429s we under rated a bit, and the net is closer to what they actually claimed.
Well I am planning on checking everything out before i put it in so I'll probably put new gaskets on and all the small stuff. I knew that they were rated for 360 hp and figured that it wouldn't be hard to get to 400. You were saying about 288 hp, Which one do you think is more accurate? Plus, will i have to run gas above 93 octane with the 11:1 compression?
They were rated 360 HP under the old gross rating system. The rule of thumb was about 80% for the later SAE net rating. 80% of 360 is 288, which seems low. HP ratings in the late '60s and early '70s were skewed by government and insurance pressures. Manufacturers would understate HP ratings so the vehicles in question would not be tagged for performance surcharges, or draw regulatory attention. The Boss 302 and Z-28 motors both test out about 360+ HP, but were both rated 290 HP. CJ 428s were rated 335 HP, while similar PI motors were rated higher:
If this engine hasn't been gone into. The exhaust valves probably don't have harden exhaust valve seats. this engine in the beginning was for leaded fuel. Today's fuel isn't leaded, unleaded. will probably have some exhaust valves sucking up in the head soon. something to be concerned about. other than that 400 hrspwr isn't hard to make with this engine at 10 to 1 comp. 1 hrspwr per cube with right cam and intake and header. mild port work on exhaust. Work the bowl area as air comes into intake valve area and good things will happen. Ran this engine for yrs, still have! Been a trooper.
Okay cool. The guy I got this off of knew nothing about it as a guy just gave it to him. I am planning on taking the heads off to give everything a look. I did drop the pan and surprisingly it looked really good. All the bearings seem nice and unsurfaced plus the timing chain was still tight like it was new. But anyhow, so you are saying that I should change the valve seats? Also could someone tell me why I CANT run pump gas with this engine?
You can run those heads and chance that they will hold up to unleaded gas. Some engines last a long time, some suffer sunken valve seats in short order. You can pull your valve covers after a couple oil changes and see if you have any "high" valves.
You can run pump gas, as long as the pump is the highest quality highest octane you can find. You may have to retard your ignition a bit and be good, or you might get pinging/detonation and have to figure something else out.
I once talked to a fellow using two head gaskets on one of these to make it run without pinging. Not sure how that worked out, but I would think that would be a guaranteed blown gasket situation.
More "radical" cams bleed off cylinder pressure enough to allow higher compression, so if you are thinking of a cam, ask the cam maker about your engine specifics.
Run it "as-is" for a while. Costs you nothing, and you'll get a feel for it on pump gas etc.
another option is since you are taking the heads off anyways, is swap them for the later D3VE heads with the bigger chambers. this will lower your compression into the 9 to 9.5 range and you will get hardened seats also. there is very little difference in port designs between the two, so performance won't suffer due to the ports. both heads really benefit from porting work especially on the exhaust side (check out Reincarnation Automotive for a guide on how to home port these heads, costs about 25 or 30 to register but well worth it).
the big difference between the heads is that the DOVE heads used screw in rocker studs with positive stop studs while the D3VE heads used bolt down pedastal style rocker arms. if keeping the D3VE rocker arm system on the DOVE block, you will have to measure for correct pushrod length. you can get them machined down to accept aftermarket studs and roller rockers or there are kits out there that convert them to adjustable roller rockers without machining.
that would be a easy way to let the motor survive easier on 93 octane gas. have a 70 460 and even on 93 octane when i step into the pedal it will ping pretty good, but under most normal driving conditions it behaves nicely on 93 octane.
I have never personally done it but Call Rich At circle R in IL. He has ran a ton of dove heads WITHOUT hard seats, even on the strip. He claims that the hard/soft seat issue is nothing more than hype created by machine shops to get a rebuild out of a guy that may not even need it. If your seats fail, I highly doubt it is because of lead/no lead. It is probably because that thing is like 45 years old. The 429 thunder jet was either 320 or 360 and the CJ was 370, The super CJ isn't even listed in my book, for HP that is, neither is the PI. The CR is specd to 10.5:1 and if that is actually correct, you might run on pump premium.
Remember that some of these engines have been torn down that didn't have 10.5:1 factory, and it has been claimed that with deck heights and gasket thicknesses, some have been found that didn't even have 10:1. If you are dead set on this, run a cam with some overlap and that will help run on our gas today. dumps some compression.
When looking at your valve seats look and see if all are even on height. harden exhaust seats will become a issue if driven a lot! I have had valves suck up. if valve sucks up into head and you don't catch you will probably drop a valve and do some serious damage. If new harden seats installed and machinist cuts into to far can cut past harden material and this will also cause your seats to wear abnormally, suckuped valves. If running agressive cams this will possibly cause things to happen quicker. things i have learned along the way over the past 20 yrs. Proper valvespring pressure is a must per cam also. good luck and 429 is a good engine i ran for many yrs. I still have mine for a spare. Run solid cams in my 429 and 472 and 520. Basically SCJ big blocks. They all make more than the factory SCJ from back in the day. The PI (police inteceptor)heads work well also with some cubic in under them, thinking 500" would be nice. have a good evening.
May be hard to run it on pump gas. I was recently dealing with a similar engine (same block and heads), but it was a 460. On 93 octane I couldn't get it to stop pinging with the vacuum advance hooked up. With the advance unhooked and the engine re-timed, it wouldn't ping, but I didn't get as good of gas mileage (like 5 mpg) and it wasn't as responsive as I would have liked.
With these engines when you go getting a little above 10:1 compression, everything has to be right to keep it on pump gas and still run it with efficiency (well, as efficient as a big block will get) on the street. The D0VE heads are good for making power, but they also get hot and can be a contributing factor for detonation. The engine I'm working with now has D3VE aluminum heads, which are also a fairly good design and dissipate heat better. These can support 600HP+ ported correctly.
If you have issues with detonation, you should also look at other factors like trying to get the coolest air into the intake. You may need to run an intake hose to your air cleaner to get cold air. You can also take the intake off (you'll be there while doing a cam swap) and block off the exhaust cross-over port to help keep the intake cooler to keep intake air temp down.
Various spark plug heat ranges can also help reduce detonation.